2 ANALYTICAL MECHANICS 2. Divisions of Mechanics. — It is customary to divide Mechanics into Kinematics and Dynamics. The former treats of the time and space relations of the motions of bodies without regard to the interactions which cause them. In other words, Kinematics is the geometry of motion. In Dynamics, on the other hand, motion and equilibrium are treated as the results of interactions between bodies; consequently not only time and space enter into dynamical discussions, but also mass, the third element of motion. Dynamics in its turn is divided into Statics and Kinetics. Statics is the mechanics of bodies in equilibrium, while Kinetics is the mechanics of bodies in motion. Chapters II, III, and IV of the present work are devoted to problems in statics, while the rest of the book, with the exception of Chapters I, V, and VII, is given to discussions of problems in kinetics. The subject matter of Chapters I and VII is essentially of a mathematical nature. In the former the addition and resolution of vectors are discussed, while in the latter the Calculus is applied to finding centers of mass and moments of inertia. Chapter V is devoted mainly to kinematical problems.